'Leap Seconds' May Be Eliminated From UTC

angry tapir writes "Sparking a fresh round of debate over an ongoing issue in time-keeping circles, the International Telecommunications Union is considering eliminating leap seconds from the time scale used by most computer systems, Coordinated Universal Time (UTC). Since their introduction in 1971, leap seconds have proved problematic for at least a few software programs. The leap second added on to the end of 2008, for instance, caused Oracle cluster software to reboot unexpectedly in some cases."

Comments

Hmmm

[HappyClown]

Now waaaaaait just one second! Oh, scratch that...

Poor solution

[LostMyBeaver]

The proper solution is to make programmers aware of leap seconds. There are 86400 seconds in a normal day, however there is an additional second added once or twice a year to adjust for solar time.

Wikipedia documents it quite well and programmers in modern times should be heading to wikipedia almost constantly anyway. The real problem occurs when the date/time is given in seconds since an "event" such as Jan 1, 1970. Most programmers don't know about leap seconds and I must admit, I don't generally bother calculating for them. But if it were necessary, it would be relatively trivial to do so.

We shouldn't remove fixes to the clock just because programmers are undereducated. I'm quite convinced that just posting this on Slashdot will raise awareness across a high percentage of the programming world.

I also always wondered why undergraduate studies for computer science didn't make time a relevant issue. It seems as if it's one of the more complex topics and yet, we don't pay any attention to it. Last formal education I had on time (not talking about physic related, but calendar) was in primary school. There are so many time systems out there that we should pay more attention to educating programmers on it.

Re:Poor solution

[Thorsett]

Why adjust for solar time?

We adjust for solar time because UTC is an astronomical timescale, not a "count of seconds since a specific time." If "computer people" want a timescale that ignores leap seconds, they can use an atomic timescale like TAI (or GPS time, which is a constant offset from TAI). But choosing to standardize the internet on UTC and then complaining it is too hard to do the programming right is a little like buying a house next door to a turkey farm and complaining about the smell.

Oracle

[Anonymous Coward]

Perhaps Oracle should concentrate more on making their software reliable, and less on lawsuits.

From what I recall Digital VMS didn't have that problem, and even had no problems migrating an always on system over different processors, and keeping the cluster running over more than 15 years. One second and Oracle crashes.

It's a pity which of those companies survived.

Re:Oracle sholuld simply fix their software...

[nacturation]

Isn't the problem with Oracle here? It should not be that difficult to fix their software. What's the difference with Summer time change?

The difference with spring/fall time changes is that although the local time may change, the UTC time does not. In other words, your offset from UTC (eg: GMT-8) may get adjusted depending on your location's observance of daylight savings time but UTC itself simply marches on oblivious to anything. The leap second is the one exception.

Ok...

[Chyeld]

Isn't this like legislating that PI is 3.14 because some people have problems with the idea of irrational numbers? If programs have issues with leap seconds, it sounds like programs weren't written properly, not that the spec needs to be rewritten to accommodate this flaw. Would these same people have demanded that it be 1999 again to avoid all the costs of the Y2K fixes?

Re:The problem with leap seconds...

[joe_frisch]

We could fix this tricky programming issue by regularly adjusting the earth's orbit....

The real problem is using seconds for everything

[Terje Mathisen]

I've worked with NTP for nearly 20 years now, and the leap second adjustments isn't a real problem.

The crux of the matter is that we've insisted (in both Unix and Windows) on measuring calendar events in seconds:

The proper solution is to use Julian Day Number as the basic unit for calendars and (SI) seconds for any kind of short-term measurement. If you really need second/sub-second precision for long-term (multi-day) measurements, then you have to accept that the conversion is not just a matter of multiplying/dividing by 86400.

Calendar appointments and similar things should be defined by day number and some form of fractional day, not SI seconds.

NTP is somewhat to blame though: Even though it has full support for leap second handling (both adding and subtracting), the core of the protocol pretends that UTC seconds (without leap adjustments) is sufficient, i.e. NTP timestamps are defined to be in a 64-bit fixed-point format with 32 bits counting seconds since 1900-01-01 and 32 bit for the fractional seconds, i.e. sufficient to handle a 136-year block with a quarter of a ns resolution.

http://www.eecis.udel.edu/~mills/ntp/html/ntpd.html#leap

This causes small hiccups for an hour or so after each adjustment: The primary servers and those that either have a leap-second aware source or a cluefull operator keep in sync throughout the adjustment, while the remainder will slowly detect that their local clocks seems to be a full second off. Since this is way more than the default +/- 128 ms which NTP is willing to handle with gradual adjustments, NTPD will instead step the clock (backwards for an added leap second) and restart the protocol engine, after discarding all history.

Modern versions of NTP have been rewritten to use a vote between all otherwise good servers: If a majority claim that there will be a leap second at the end of the current day, then the local deamon will believe them, and thereby stay in sync even during the actual leap second itself.

Terje

Let's see if I've got this right

[Joce640k]

We have to make every clock in the world inaccurate because Oracle's software is crap...?

Re:Let's see if I've got this right

[stdarg]

Eh, let a future generation fix Oracle's code.

Re:Let's see if I've got this right

[Kjella]

Daylight Savings has had numerous studies showing reduced electricity consumption.

Yes, the question is more if there's more or less hassle to have summer and winter opening hours than to change "time" itself.

Re:Let's see if I've got this right

[AltairDusk]

Flight industry and safety equipment also goes through very stringent testing. If the capability to handle leap seconds isn't included in their battery of tests then they have a hole in their testing procedure.

Re:Let's see if I've got this right

[cizoozic]

Leap seconds, in contrast, are completely pointless. They exist because the SI day is slightly shorter than the solar day, by a tiny fraction of a second. This means that, after a few years, the sun will not quite be at its apex precisely at midday. How much is the variation? We've had 24 leap seconds since they were introduced in 1972, but a lot of these were to slowly correct the already-wrong time. In the last decade, we've had two. At that rate, it will take 300 years for the sun to be a minute off. It will take 18,000 years for it to be an hour off. These numbers are slightly wrong. The solar day becomes a bit under 2ms longer every hundred years, so we'd need leap seconds more often later.

Well in that case it's probably easier for Oracle to just buy the Sun.

Re:Stupid

[bickerdyke]

Why abolish it?

You're free to CHOOSE your timescale! GPS, UTC, UT1, TIA.....

So if leap seconds confuse you, use a timescale without them. Thats what they're for. But keep the timescale that's supposed to be in sync with earth rotation in sync with earth rotation!